1. Field of the Invention
The present invention relates to a ceramic circuit board and an electronic device, and in particular, relates to a ceramic circuit board, which is suitable for use as an insulating substrate for a power semiconductor, for example, of a bipolar transistor, a power MOSFET (metal-oxide-semiconductor field-effect transistor), an IGBT (Insulated Gate Bipolar Transistor) or the like, as well as to an electronic device utilizing such a ceramic circuit board.
2. Description of the Related Art
In recent years, for example as shown in FIG. 3A, a ceramic circuit board 100 having a first metal plate 104 on a front surface 102a of a ceramic substrate 102, and a second metal plate 106 on a rear surface 102b of the ceramic substrate 102, has been used as an insulating substrate for a power semiconductor (for example, see Japanese Patent No. 3847954). In addition, an electronic device 112 may be constituted by mounting a power semiconductor 108 through a bonding layer 110, for example, such as solder or the like, on the first metal plate 104, as shown in FIG. 3B.
In the ceramic circuit board 100 on which the power semiconductor 108 is mounted, for suppressing generation of heat, a high heat dissipation property is required. Accordingly, in general, for use as the first metal plate 104 and the second metal plate 106, metal plates that exhibit high thermal conductivity, including Cu (copper) and Al (aluminum), are selected. For the ceramic substrate 102, a ceramic substrate that exhibits high thermal conductivity, such as AlN (aluminum nitride) or Si3N4 (silicon nitride), is selected. A heat dissipating substrate, in which the aforementioned materials are bonded directly or are bonded through a brazing material, is used as a ceramic circuit board 100.
In particular, with the ceramic circuit board 100, in which a first metal plate 104 and a second metal plate 106 constituted from Cu, and a ceramic substrate 102 constituted from Si3N4 are joined through a brazing material, due to the ceramic, which possesses high strength, and Cu, which exhibits high thermal conductivity, the ceramic circuit board 100 is superior in terms of heat cycle characteristics and thus can be utilized advantageously. Further, a heat sink, for example, may be bonded to an end surface of the second metal plate 106.